# Tutorial Build and Run a Simple Gameserver (C++) > This tutorial describes how to use the Agones C++ SDK in a simple C++ gameserver. --- LLMS index: [llms.txt](/site/llms.txt) --- ## Objectives - Run a simple gameserver - Understand how the simple gameserver uses the Agones C++ SDK - Build a customized version of the simple gameserver - Run your customized simple gameserver ## Prerequisites 1. [Docker](https://www.docker.com/get-started/) 2. Agones installed on GKE 3. kubectl properly configured 4. A local copy of the [Agones repository](https://github.com/agones-dev/agones/tree/release-1.58.0) 5. A repository for Docker images, such as [Docker Hub](https://hub.docker.com/) or [GC Container Registry](https://cloud.google.com/container-registry/) To install on GKE, follow the install instructions (if you haven't already) at [Setting up a Google Kubernetes Engine (GKE) cluster](/site/docs/installation/creating-cluster/gke/). Also complete the "Installing Agones" instructions on the same page. While not required, you may wish to review the [Create a Game Server](/site/docs/getting-started/create-gameserver/), [Create a Game Server Fleet](/site/docs/getting-started/create-fleet/), and/or [Edit a Game Server](/site/docs/getting-started/edit-first-gameserver-go/) quickstarts. ### 1. Run the simple gameserver First, run the pre-built version of the simple gameserver and take note of the name that was created: ```bash kubectl create -f https://raw.githubusercontent.com/googleforgames/agones/release-1.58.0/examples/cpp-simple/gameserver.yaml GAMESERVER_NAME=$(kubectl get gs -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}') ``` The game server sets up the Agones SDK, calls `SDK::Ready()` to inform Agones that it is ready to serve traffic, prints a message every 10 seconds, and then calls `SDK::Shutdown()` after a minute to indicate that the gameserver is going to exit. You can follow along with the lifecycle of the gameserver by running ```bash kubectl logs ${GAMESERVER_NAME} cpp-simple -f ``` which should produce output similar to ``` C++ Game Server has started! Getting the instance of the SDK! Attempting to connect... ...handshake complete. Setting a label Starting to watch GameServer updates... Health ping sent Setting an annotation Marking server as ready... ...marked Ready Getting GameServer details... GameServer name: cpp-simple-tlgzp Running for 0 seconds ! GameServer Update: name: cpp-simple-tlgzp state: Scheduled GameServer Update: name: cpp-simple-tlgzp state: RequestReady GameServer Update: name: cpp-simple-tlgzp state: RequestReady GameServer Update: name: cpp-simple-tlgzp state: Ready Health ping sent Health ping sent Health ping sent Health ping sent Health ping sent Running for 10 seconds ! Health ping sent ... GameServer Update: name: cpp-simple-2mtdc state: Ready Shutting down after 60 seconds... ...marked for Shutdown Running for 60 seconds ! Health ping sent GameServer Update: name: cpp-simple-2mtdc state: Shutdown GameServer Update: name: cpp-simple-2mtdc state: Shutdown Health ping failed Health ping failed Health ping failed Health ping failed Running for 70 seconds ! Health ping failed Health ping failed Health ping failed Health ping failed Health ping failed Running for 80 seconds ! Health ping failed Health ping failed Health ping failed Health ping failed Health ping failed ``` If everything goes as expected, the gameserver will exit automatically after about a minute. In some cases, the gameserver goes into an unhealthy state, in which case it will be restarted indefinitely. If this happens, you can manually remove it by running ```bash kubectl delete gs ${GAMESERVER_NAME} ``` ### 2. Run a fleet of simple gameservers Next, run a fleet of gameservers ```bash kubectl create -f https://raw.githubusercontent.com/googleforgames/agones/release-1.58.0/examples/cpp-simple/fleet.yaml FLEET_NAME=$(kubectl get fleets -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}') ``` You can again inspect the output of an individual gameserver (which will look the same as above), but what is more interesting is to watch the set of all gameservers over time. Each gameserver exits after about a minute, but a fleet is responsible for keeping a sufficient number of gameservers in the `Ready` state. So as each gameserver exits, it is replaced by a new one. You can see this in action by running ```bash watch "kubectl get gameservers" ``` which should show how gameservers are constantly transitioning from `Scheduled` to `Ready` to `Shutdown` before disappearing. When you are finished watching the fleet produce new gameservers you should remove the fleet by running ```bash kubectl delete fleet ${FLEET_NAME} ``` ### 3. Build a simple gameserver Change directories to your local agones/examples/cpp-simple directory. To experiment with the SDK, open up `server.cc` in your favorite editor and change the interval at which the gameserver calls `SDK::Health` from 2 seconds to 20 seconds by modifying the line in `DoHealth` to be ```c++ std::this_thread::sleep_for(std::chrono::seconds(20)); ``` Next build a new docker image by running ```bash cd examples/cpp-simple REPOSITORY= # e.g. gcr.io/agones-images make build REPOSITORY=${REPOSITORY} ``` The multi-stage Dockerfile will pull down all of the dependencies needed to build the image. Note that it is normal for this to take several minutes to complete. Once the container has been built, push it to your repository ```bash docker push ${REPOSITORY}/cpp-simple-server:0.6 ``` ### 4. Run the customized gameserver Now it is time to deploy your newly created gameserver container into your Agones cluster. First, you need to edit `examples/cpp-simple/gameserver.yaml` to point to your new image: ```yaml containers: - name: cpp-simple image: $(REPOSITORY)/cpp-simple-server:0.6 imagePullPolicy: Always # add for development ``` Then, deploy your gameserver ```bash kubectl create -f gameserver.yaml GAMESERVER_NAME=$(kubectl get gs -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}') ``` Again, follow along with the lifecycle of the gameserver by running ```bash kubectl logs ${GAMESERVER_NAME} cpp-simple -f ``` which should produce output similar to ``` C++ Game Server has started! Getting the instance of the SDK! Attempting to connect... ...handshake complete. Setting a label Health ping sent Starting to watch GameServer updates... Setting an annotation Marking server as ready... ...marked Ready Getting GameServer details... GameServer name: cpp-simple-f255n Running for 0 seconds ! GameServer Update: name: cpp-simple-f255n state: Scheduled GameServer Update: name: cpp-simple-f255n state: Scheduled GameServer Update: name: cpp-simple-f255n state: RequestReady GameServer Update: name: cpp-simple-f255n state: Ready Running for 10 seconds ! GameServer Update: name: cpp-simple-f255n state: Unhealthy Health ping sent Running for 20 seconds ! GameServer Update: name: cpp-simple-f255n state: Unhealthy Running for 30 seconds ! Health ping sent Running for 40 seconds ! Running for 50 seconds ! GameServer Update: name: cpp-simple-f255n state: Unhealthy Health ping sent Shutting down after 60 seconds... ...marked for Shutdown Running for 60 seconds ! Running for 70 seconds ! Health ping sent Running for 80 seconds ! GameServer Update: name: cpp-simple-f255n state: Unhealthy Running for 90 seconds ! Health ping sent ``` with the slower healthcheck interval, the gameserver gets automatically marked an `Unhealthy` by Agones. To finish, clean up the gameserver by manually removing it ```bash kubectl delete gs ${GAMESERVER_NAME} ```